A senior Greek police officer has claimed that the far-right Golden Dawn party has infiltrated the police at various levels. He has laid the blame on consecutive governments and the leadership of the police force for turning a blind eye to what he describes as “pockets of fascism”.

Speaking to the Guardian on condition of anonymity, the officer said the Greek state had been fully aware of the activities of Golden Dawn for several years, with the National Intelligence Service and other security agencies monitoring it closely. The officer claimed police chiefs had had the opportunity to isolate and remove these small “pockets of fascism” in the force but decided not to. The state, he said, wanted to keep the fascist elements “in reserve” and use them for its own purposes.

The officer said he believed that Golden Dawn members could be used against the Greek left, which has led popular street protests against the government and austerity measures imposed by the EU. He expressed his belief that neo-fascist groups may already have acted as agents provocateurs during demonstrations across the country, to provoke clashes between demonstrators and the police or even between demonstrators themselves.

A spokesman for the Greek police, Christos Manouras, denied the police were using or being used by “any political formation against any other”. Manouras rejected the existence of “pockets of fascism” within the force and said no unlawful behaviour would be tolerated.

He conceded that “individual cases can be found everywhere and at any workplace”. But he added: “It is unfair for the Greek police force to be accused with no evidence that they tolerate or support specific actions or to be identified with certain [political] beliefs … You should note that – in accordance with the constitution and laws of the Greek republic – only illegal acts can be prosecuted and punished. The same does not apply for political positions, even if characterised as ‘extreme’ by the other parties and the overwhelming majority of public opinion.”

Golden Dawn won 6.9% of the vote in elections in June, taking 18 seats in parliament, but a recent opinion poll conducted by research company VPRC suggested the party had doubled its support since then.

Human rights groups have accused the Greek police of being sympathetic to, or acting in collusion with, the group, and earlier this week a report of the Racist Violence Recording Network, a group consisting of 23 NGOs and the UN high commissioner for refugees, highlighted violent incidents in which police and racist violence overlapped.

“These incidents concern duty officers who resort to illegal acts and violent practices while carrying out routine checks,” says the report. “There are also instances where people were brought to police stations, were detained and maltreated for a few hours, as well as cases where legal documents were destroyed during these operations.”

Kostis Papaioannou, former head of the Greek national commission for human rights, said: “On some occasions there is a blurred line between Golden Dawn and the police.” Allegations of collusion resurfaced after anti-fascist protesters told the Guardian they had been “tortured by police” after clashes with Golden Dawn supporters. The minister of public order, Nikos Dendias, has denied the allegations.

The officer who spoke to the Guardian accused the government of abandoning Greek police officers and thus creating the conditions for Golden Dawn to infiltrate the force. “These policemen feel unappreciated and isolated. They are badly paid, they work under the worst conditions and they look for support,” he said, adding that they found it among the neo-Nazi community.

He also called on the ministry of public order to disclose reports of the internal affairs division, which he said showed cases of police brutality. “We should never accept policemen who attack journalists from behind,” he said, referring to an attack on the president of the Greek photojournalists’ union, who was taken to hospital with a brain injury last May.

The press officer of the Hellenic police restated the ministry’s commitment to establishing a special response team to combat racist violence.

Several cases of violent attacks carried out in the presence of Golden Dawn MPs have been reported recently, including the storming of flea markets and an incident in which stones were thrown, and racist abuse hurled, at audience members during the Athens premiere of Terrence McNally’s play Corpus Christi.

Earlier this year, Liana Kanelli, an outspoken Communist party MP, was assaulted during a live TV talkshow by Ilias Kasidiaris, Golden Dawn’s spokesman, in an incident that made headlines around the world.

This week the Greek parliament voted in favour of lifting the immunity of three Golden Dawn MPs who could now face trial for suspected violent attacks and allegedly assisting in a robbery. Among them is Kasidiaris, who has claimed he is the victim of political persecution.

Kanelli characterised Golden Dawn as an “ideological and political pimp” serving “a mission that the system assigned to it”. According to Kanelli, immigrants were just the first victims of the party, which also threatens workers and has attempted to infiltrate unions.

“If an employer wants to blackmail you, he threatens to call Golden Dawn,” said Javed Aslam, a leader of the Pakistani community in Greece.